This invention relates to a bimetal and more particularly to a bimetal which is rapidly deflected at an optionally specified high temperature and indicates a satisfactory reversible behavior depending on temperature change.
The deflection of the prior art bimetal generally proceeds at a substantially fixed rate in proportion to temperature change. Where, therefore, it was desired to use the known bimetal in such application as required the bimetal to make a rapid deflection over a prescribed temperature range, for example, the application where a bimetal was directly used in a contact drive mechanism, it was necessary to provide an additional quick responsive drive mechanism. The quick responsive drive mechanism includes, for example, a repulsion board, magnet or spring. A combination of a bimetal and any of these quick responsive drive mechanisms enabled the original slow deflection of the bimetal itself to be carried out quickly. However, a bimetal device which was provided with the above-mentioned quick responsive drive mechanism had the drawbacks that the bimetal device as a whole becomes bulky and had to be manufactured with a complicate design.
The known bimetal indicating a rapid deflection over a certain temperature range includes martensite transformation such as an Ni-Ti alloy utilizing a shape memory effect. This shape memory type alloy has to be deformed under a specified temperature condition before being used as a bimetal. And, said shape memory type alloy does not indicate the same rate of deflection when used frequently, failing to be effectively used in practice. Moreover, the above-mentioned type of bimetal had the drawbacks that it indicated a rapid deflection at a relatively low temperature, and had insufficient workability and bandability, presenting difficulties in manufacture.
A bimetal rapidly deflectable at a specified temperature is generally used for temperature control of household electric appliances and as a safety device for various industrial apparatuses. Therefore, the above-mentioned bimetal is desired to have as high an anticorrosive property as possible.